I have been asked to apply a really thick layer of conformal coating to my printed circuit board. What are the problems with this approach?
Applying conformal coating really thick is not a good idea especially if you exceed the recommended thickness from the manufacture.
There are several reasons for this but the two key ones are:
- Applying a thick coating can cause long-term reliability issues. This is because the conformal coating can crack and craze in the long-term. It can also possibly cause damage to the PCB due to Coefficient of Thermal Expansion (CTE) mismatch between components and the coating.
- Defects like bubbles can occur when applying really thick conformal coating layers.
If in doubt, more is not better. Conformal coatings are not designed as encapsulates and potting compounds. The IPC and mil spec recommend certain thicknesses such as 30-150um for acrylics. It’s a good idea to keep within these tolerances and use conformal coating thickness measurement systems to check.
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